Investment Securities - Summary (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Available-for-sale debt securities:
Cost	$ 1,203
Estimated Fair Value	1,192	$ 2,120
Equity securities
Cost	53	60
Gross Unrealized Gains	4	16
Gross Unrealized Losses	(9)	(10)
Estimated Fair Value	48	66
Total Cost	1,256	2,198
Total Gross Unrealized Gains	5	17
Total Gross Unrealized Losses	(21)	(29)
Total Estimated Fair Value	1,240	2,186
New public companies
Equity securities
Cost	3
Estimated Fair Value	7
State and municipal obligations
Available-for-sale debt securities:
Cost	57	61
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(9)	(6)
Estimated Fair Value	49	55
U.S. Government agency obligations
Available-for-sale debt securities:
Cost	4	4
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	4	4
U.S. Government treasury obligations
Available-for-sale debt securities:
Cost	289	1,217
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(2)	(12)
Estimated Fair Value	287	1,206
Mortgage-backed securities
Available-for-sale debt securities:
Cost	11	12
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	10	11
Foreign government bonds and obligations
Available-for-sale debt securities:
Cost	765	770
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	765	770
Other
Available-for-sale debt securities:
Cost	77	74
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 77	$ 74